1. Field of the Invention
The present invention relates to a technique for detecting minute foreign particle and defect that might be found on a thin film substrate, a semiconductor substrate or a photomask and so forth.
2. Description of the Prior Art
In the production line of a semiconductor substrate or a film substrate and so on, detection is carried out for foreign particle that is attached on the same substrates so as to monitor the dust contamination in ambient caused by the production apparatus. For instance, it is required to detect such minute foreign particle and defect as is below 0.1 lm in size on the surface of the semiconductor substrate before circuit layout is formed thereon. As one example of the prior art for detecting minute foreign particle and defect on such sample object as the semiconductor substrate, it is disclosed in the specification of the U.S. Pat. No. 5,798,829 that laser beams that are converged within the range from a few lm to several tens of xcexcm are irradiated against a sample object and scattered light, which is generated from foreign particle when the same matter attaches on the substrate, is detected and the foreign particle and defect on the whole surface of the sample object are detected through the revolution as well as the rectilinear forwarding of the same object.
Further, such concave defects as crystal defect and scratches are found on the surface of the semiconductor substrate. In order to separately detect such concave defects from convex such defect as foreign particle, it is disclosed in Japanese Patent Application Laid-open Nos. 9-304289 and 9-210918 that detection is carried out by changing the irradiation angle of the laser beams or detection angle with regard to a sample object and the detection results are compared so as to classify the defects into some categories.
In accordance with the trend for the high density and large caliber of a semiconductor substrate, a thin film substrate or a photomask and so forth, the means to detect foreign particle and defect on the surface thereof require high sensitivity and high speed for detection. Further, in accordance with the trend for the high density of the semiconductor substrate (semiconductor wafer), the thin film substrate or the photomask and so forth, leveling operation by means of CMP (Chemical Mechanical Polishing) is performed thereon for the purpose of abating the load charged by the depth of focus of an exposure device, in which operation such minute defect as called scratch happens to occur on the surface of the substrate and so forth. The countermeasure taken against the scratch and that against the foreign particle differ, so that it is required to separately detect such scratch from the foreign particle.
The present invention is intended to reduce the number of detection steps so as to perform the detection for a short period of time and to scan a sample object in detection with high speed as well as to accurately grasp the situation of foreign particle and defect with high sensitivity and to separately and precisely detect on such sample object as a semiconductor wafer such defect as scratch from the foreign particle.
The present invention provides a method for detecting foreign particle and defect and the same apparatus that realize the above purposes.
That is, in this invention, the situation of foreign particle and defect is discerned according to a signal obtained by converting the scattered light of every wavelengths that emits from a sample object into an electric signal upon the irradiation of the plurality of laser beams with different wavelengths with regard to practically the same location of a sample object from different angles. Further, it is arranged such that the laser beams are irradiated onto the sample object from the sole location or several locations and the scattered light emitted from the sample object is detected at several directions, the result of which detection is compared so as to detect the directivity of the scattered light, according to which directivity the foreign particle or defect is separately detected. The above operational steps allow the detection to be carried out with high speed as well as high sensitivity and to separately detect such defect as scratch from foreign particle.